Problems in using linear ultrasound parameters for the determination of fetal weight

We have developed three formulas for the calculation of fetal weight by means of ultrasound which have proved clinically useful (Formula I for normal size fetuses, Formula II for very small fetuses, and Formula III as a control). From 621 controlled calculations of the fetal weight and the general experience from our ultrasound clinic (over 20,000 examinations) we discuss the inherent problems. We used the Vidoson apparatus manufactured by Siemens (West Germany) which is a rapid imaging B-scan. We have learned from many years of studying means of calculating fetal weight that a regression equation from linear fetal measurements can be used: namely the biparietelllll skull diameter, the sagittal and the transverse thoracic diameter and the length of the trunk (Tab. I)...